Needle bar driver assembly for a sewing machine

ABSTRACT

There is provided a needle bar driver assembly for an overlock sewing machine. The overlock sewing machine has a needle for penetrating a material to be sewed, a needle bar for securing the needle thereto, and a throat plate for allowing the needle to pass there through. The needle bar driver assembly includes a needle bar connecting link assembly for driving the needle bar. The needle bar driver assembly further includes an oscillating needle bar driving assembly for driving the needle bar connecting link assembly and for raising said needle bar connecting link assembly such that the needle is more than 18 mm above the throat plate.

FIELD OF THE INVENTION

[0001] The present invention generally relates to sewing machines and, more particularly, to a needle bar driver assembly for a sewing machine.

BACKGROUND OF THE INVENTION

[0002] Conventional sewing machines employ a solid driver bar that drives the needle bars, and hence the needles, in an oscillating motion. However, the use of a solid driver bar limits the upper travel limit of the needle bars, and hence the needles, making it difficult for an operator to insert and remove thick materials during a sewing operation.

[0003] Accordingly, it would be desirable and highly advantageous to have a needle bar driver assembly that extends the upper travel limit of the needle bar, and hence the needles, to reduce the difficulties associated with inserting and removing thick materials during a sewing operation.

SUMMARY OF THE INVENTION

[0004] The problems stated above, as well as other related problems of the prior art, are solved by the present invention, a needle bar driver assembly for a sewing machine.

[0005] According to an aspect of the present invention, there is provided a needle bar driver assembly for an overlock sewing machine. The overlock sewing machine has a needle for penetrating a material to be sewed, a needle bar for securing the needle thereto, and a throat plate for allowing the needle to pass there through. The needle bar driver assembly comprises a needle bar connecting link assembly for driving the needle bar. The needle bar driver assembly further comprises an oscillating needle bar driving assembly for driving the needle bar connecting link assembly and for raising said needle bar connecting link assembly such that the needle is more than 18 mm above the throat plate.

[0006] According to another aspect of the present invention, there is provided a method for controlling a needle of an overlock sewing machine. The needle is for penetrating a material to be sewed. The overlock sewing machine further includes a needle bar for securing the needle thereto, and a throat plate for allowing the needle to pass there through. The method comprises the steps of driving the needle bar, and raising the needle bar such that the needle is more than 18 mm above the throat plate.

[0007] These and other aspects, features and advantages of the present invention will become apparent from the following detailed description of preferred embodiments, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a diagram illustrating a needle bar driver assembly 100 in a locked condition, according to an illustrative embodiment of the present invention;

[0009]FIG. 2 is a diagram illustrating the interior of a needle bar drive chamber 200 that includes the needle bar driver assembly 100 shown in FIG. 1, according to an illustrative embodiment of the present invention;

[0010] FIGS. 3A-C are diagrams generally illustrating the unlocking of the needle bar driving assembly 101 shown in FIG. 1, according to an illustrative embodiment of the present invention; and

[0011]FIG. 4 is a diagram illustrating the needle bar driver assembly 100 of FIG. 1 in an unlocked condition, according to an illustrative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention is directed to a needle bar driver assembly for a sewing machine. Advantageously, the present inventions allows for thick, quilted materials to be sewn by raising the upper travel limit of the needle and presser foot of the sewing machine. The present invention accomplishes the preceding without affecting (slowing down) the speed of the sewing machine.

[0013] It is to be appreciated that the present invention is directed to “overlock” types of sewing machines, which are also referred to as, for example, “overedge”, “overcast”, “overhead”, and “serger” type sewing machines. For the purposes of the present invention, it is presumed that a sewing machine to which the present invention is to be applied includes or is adapted to be able to include a presser foot assembly for raising and lowering a presser foot, a looper for manipulating a thread, a needle for penetrating a material to be sewed, and a throat plate for allowing the needle to pass there through. The presser foot is for pressing down on the material to be sewed.

[0014] In one embodiment of the present invention, the present invention includes a needle bar for securing the needle thereto and a needle bar connecting link assembly for driving the needle bar. Moreover, the present invention includes an oscillating needle bar driving assembly for driving the needle bar connecting link assembly in synchronization with a timing of the looper and for raising the needle bar connecting link assembly such that the needle is more than 18 mm above the throat plate. A presser foot assembly raises the presser foot a distance corresponding to the distance at which the needle is raised. The correspondence between the distances at which the needle and presser foot are lifted is necessary to prevent the needle from sticking through the bottom plane of the presser foot and tearing the material that is to be sewed. It is to be appreciated that while a distance of more than 18 mm is used herein as the example distance from the needle and presser foot to the throat plate, even greater distances (20, 22, 24, 27, 30, 40, and so forth) may be readily achieved by the present invention as is apparent to one of ordinary skill in the art given the teachings of the present invention provided herein.

[0015] As is known, the presser foot assembly includes a presser foot (also interchangeably referred to herein as “material clamp”) that is connected to a presser foot arm. The presser foot arm is also connected to a carriage. The carriage is connected to a slide or actuating cylinder. The slide is connected to a main casting (main body) of the sewing machine. The preceding presser foot assembly provides linear displacement of the presser foot. As is also known, radial displacement of the presser foot may also be employed. In the case of radial displacement, the carriage is replaced by a pivot block to provide angular (radial) displacement of the presser foot. The present invention may be used with the preceding types or any type of presser foot assembly, while maintaining the spirit and scope of the present invention.

[0016] More detailed descriptions of various aspects of the present invention will now be given with respect to FIGS. 1-5 below.

[0017]FIG. 1 is a diagram illustrating a needle bar driver assembly 100 in a locked condition, according to an illustrative embodiment of the present invention. A driver bar assembly 101 (hereinafter interchangeably referred to as “4 bar assembly”) transfers oscillating motion from a main rocking shaft (not shown) to needle bar connecting links 115, that in turn drive needle bars 120 (and, thus, needles 125) upwards and downwards at their prescribed angle. It is to be appreciated that the prior art employs a solid driver bar. In contrast, the present invention breaks up the driver bar into a locking (and unlocking) 4 bar linkage, that when unlocked, allows the upper most limit of needle bars 120 and, hence, needles 125 coupled thereto, to be extended a significant angular distance. This increased secondary lift dramatically reduces the difficulties (and secondary consequences) associated with inserting and removing the thick quilted materials associated with this sewing operation. The 4 bar assembly 101 includes an upper link 102, a main beam 104, an outer link 106, and a coupling link 108. It is to be appreciated that while the 4 bar linkage described herein includes 4 bars, hence the name, more or less than 4 bars may be employed, as contemplated by one of ordinary skill in the related art, to lift the needles a greater distance than that obtained by the prior art.

[0018] The opening of 4 bar assembly 101 is achieved through a first actuating cylinder 130 (hereinafter interchangeably referred to a “lifting cylinder”) and associated lifting shelf 132 attached to the end of a piston 135 movably disposed in lifting cylinder 130. The sewing machine is programmed to stop with the needles at their highest angular position. At this time, when actuated by the operator, the lifting shelf 132 is raised upwards, unlocking a locking latch 141 and immediately following upper link 102 of the 4 bar assembly 101 (see FIG. 2). The locking latch 141 (hereinafter also referred to as “latch”) includes a top ledge 142 coupled to a bottom catch 144 (hereinafter “catch”) via an intermediate member 146. The locking latch 141 is coupled to upper link 102 via a connecting member 199. However, in another embodiment of the present invention, locking latch 141 is directly coupled to upper link 102. Moreover, in yet another embodiment of the present invention, the physical structure and function represented by connecting member 199 may be incorporated into either locking latch 141 and/or upper link 102.

[0019] An opposing spring 155 and spring block 156 shown in FIG. 1 are described in detail below with respect to FIGS. 2 and 4.

[0020]FIG. 2 is a diagram illustrating the interior of a needle bar drive chamber 200 that includes the needle bar driver assembly 100 shown in FIG. 1, according to an illustrative embodiment of the present invention. Observe the now visible catch 144 of locking latch 141 that once held upper link 102 of 4 bar assembly 101 locked downwards to main beam 104 of 4 bar assembly 101.

[0021] The spring block 156 is coupled to the needle bar drive chamber 200 to provide a solid base from which opposing spring 155 can push away from. Needles 125 are shown coupled to needle bars 120.

[0022] FIGS. 3A-C are diagrams generally illustrating the unlocking of the needle bar driving assembly 101 shown in FIG. 1, according to an illustrative embodiment of the present invention. FIG. 4 is a diagram illustrating the needle bar driver assembly 100 of FIG. 1 in an unlocked condition, according to an illustrative embodiment of the present invention.

[0023] When lifting shelf 132 is raised, it first hits top ledge 142 of locking latch 141, relieving the spring pressure and pivoting catch 144 to the left and upwards, away from main beam 104 of 4 bar assembly 101 (see FIG. 3A).

[0024] Once catch 144 is free, lifting shelf 132 continues to lift upper link 102, breaking 4 bar assembly 101 open (see FIGS. 3B and 3C). Observe the open condition of assembly 101, and how the outer most link 106 attached to needle bar connecting link 115 raises needle bar connecting links 115 and needle bars 120 an additional angular distance (see FIG. 4). The coupling link 108 operatively couples upper link 102 to outer link 106, so that the lifting of upper link 102 results in a corresponding lifting of outer link 106 away from main beam 104. Fully, upper link 102 and outer link 106 are operatively coupled together such that the position of outer link 106 tracks the position of upper link 102. In the illustrative embodiment of the present invention, a tongue and groove structure is employed to provide positional tracking between outer link 106 and upper link 102. The tongue and groove structure is disposed between coupling link 108 and outer link 106. As is known to one of ordinary skill in the related art, the tongue portion and the groove portion of the tongue and groove structure may be readily disposed on coupling link 108 and outer link 106, respectively, or vice versa, depending on, for example, the shape (e.g., concave, convex) of the tongue portion. It is to be appreciated that while a tongue and groove structure are described herein for enabling the tracking of the outer link position to the upper link position, other structures may be readily used to achieve the same position tracking result as are readily contemplated by one of ordinary skill in the related art, while maintaining the spirit and scope of the present invention.

[0025] This motion is synchronized with the lifting of a material clamp (not shown), allowing the operator to insert or remove the material as needed. As long as the operator's foot is actuating the sewing pedal backwards (not shown) the sewing machine will remain in this condition.

[0026] The opposing spring 155 and spring block 156 apply pressure to outer link 106 of 4 bar assembly 101, acing as a compressive stop. This spring 155 will also encourage outer link 106 to rotate back into its locked position, as well as prevent outer link 106 from over rotating and locking 4 bar assembly 101 in an “open” condition.

[0027] A second actuating cylinder 160 (hereinafter interchangeably referred to as locking cylinder) and its associated piston 165 are shown in FIG. 4. When the operator releases the sewing pedal (not shown), second actuating cylinder 160 actuates piston 165 downwards to its lowest “docking” point. At this extent of its limit, lifting shelf 132 will not interfere with oscillating 4 bar assembly 101.

[0028] The 4 bar assembly 101 would remain open, however, and unlocked, if not for locking cylinder 160. When piston 165 of locking cylinder 160 actuates downwards, piston 165 depresses the top ledge 142 of the locking latch 141, and consequently, upper bar 102 of 4 bar assembly 101. Piston 165 continues to depress latch 141 until catch 144 locks beneath the lower plane of main beam 104 of 4 bar assembly 101. This actuation is momentary, releasing and raising upwards (and remaining there) fractions of a second after it locks the mechanism. When 4 bar assembly 101 is locked, and locking cylinder 160 is fully retracted, the sewing machine operator proceeds and runs the machine through its cycle. The 4 bar driving assembly 101 remains locked until the unit stops and performs its lifting cycle once again.

[0029] Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one of ordinary skill in the related art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as defined by the appended claims. 

What is claimed is:
 1. A needle bar driver assembly for an overlock sewing machine having a needle for penetrating a material to be sewed, a needle bar for securing the needle thereto, and a throat plate for allowing the needle to pass there through, the needle bar driver assembly comprising: a needle bar connecting link assembly for driving the needle bar; and an oscillating needle bar driving assembly for driving the needle bar connecting link assembly and for raising said needle bar connecting link assembly such that the needle is more than 18 mm above the throat plate.
 2. The needle bar driver assembly of claim 1, wherein the overlock sewing machine further has a looper for manipulating a thread, and said oscillating needle bar driving assembly drives the needle bar connecting link assembly such that the needle is synchronized with a timing of the looper.
 3. A method for controlling a needle of an overlock sewing machine, the needle for penetrating a material to be sewed, the overlock sewing machine further including a needle bar for securing the needle thereto, and a throat plate for allowing the needle to pass there through, the method comprising the steps of: driving the needle bar; and raising the needle bar such that the needle is more than 18 mm above the throat plate.
 4. The method of claim 3, wherein the overlock sewing machine further comprises a looper for manipulating a thread, and said driving step comprises the step of driving the needle bar in synchronization with a timing of the looper such that the needle is synchronized with the timing of the looper.
 5. A needle bar driver assembly for an overlock sewing machine, comprising: a needle bar connecting link assembly, for driving a needle bar; and an oscillating multi-part needle bar driving assembly, capable of being in a closed condition and an open condition, for transferring oscillatory motion to said needle bar connecting link assembly in the closed condition and for lifting the needle bar connecting link assembly to extend an upper travel limit of said needle bar connecting link assembly in the open condition.
 6. The needle bar driver assembly of claim 5, wherein said oscillating multi-part driver bar assembly comprises an upper link, an outer link, a coupling link, and a main beam, the upper link and the outer link both rotatably coupled to the main beam, the outer link further rotatably coupled to said needle bar connecting link assembly, the upper link and the outer link further operatively coupled together via the coupling link such that a position of the outer link tracks the position of the upper link, said oscillating multi-part driver bar assembly capable of being in the closed condition corresponding to a closed position of the upper link with respect to the main beam and capable of being in an open condition corresponding to an open position of the upper link with respect to the main beam.
 7. The needle bar driver assembly of claim 6, wherein the upper link and the outer link are operatively together by the coupling link using a tongue and groove structure.
 8. The needle bar driver assembly of claim 7, wherein the tongue and groove structure is disposed between the coupling link and the outer link.
 9. The needle bar driver assembly of claim 5, further comprising: an opposing spring, connected to the oscillating multi-part driver bar assembly, for applying downward pressure to the oscillating multi-part driver bar assembly to at least one of limit an upper travel limit of the oscillating multi-part driver bar assembly, encourage the oscillating multi-part driver bar assembly to rotate back into the closed condition, and prevent the oscillating multi-part driver bar assembly from locking in the open condition.
 10. The needle bar driver assembly of claim 5, further comprising an actuator for alternately placing the oscillating multi-part driver bar assembly into the open condition and the closed condition. 